1. Field of the Invention
The present invention relates to a method for controlling shifts of an auto vehicle transmission and more particularly to a method for controlling shifts of an auto vehicle transmission which reduces a shifting shock generated at the time of a Rxe2x86x92D range switch of the shift lever to run the vehicle forwards while it is running backwards.
2. Brief Description of the Related Art
In general, an auto transmission of a vehicle has a transmission control unit (hereinafter referred to as TCU) to automatically control a transmission rate according to the running speed and load of a vehicle.
At this time, the TCU controls the revolution number of an output terminal of a planetary gear apparatus by controlling a plurality of clutches and a brake installed at a gear train to an operational or non-operational state.
In controlling the output terminal, the TCU outputs a transmission rate controlling duty control signal, which shifts an auto transmission of a vehicle without a shock according to predetermined program processing steps when signals of various sensors to be variably output according to the running state of a vehicle to a solenoid valve which controls the oil pressure of a plurality of clutches and a brake installed at the gear drain, thereby controlling the duty of the solenoid valve and turning on or off.
First of all, in FIG. 1, C1, C2, C3, C4 and C5 respectively designate rear clutch (R/C), front clutch (F/C), low reverse brake (L/R-B), end clutch (E/C) and kick down servo (K/D).
Also, reference numerals 31, 32, 33, 34 and 35 respectively designate oil pressure control solenoid valve-A (PCSV-A), oil pressure control solenoid valve-B (PCSV-B), shift control solenoid valve-A (SCSV-A), shift control solenoid valve-B (SCSV-B) and shift control solenoid valve-C (SCSV-C).
Furthermore, reference numerals 40, 41, 42, 50, 51, 52, 53 and 54 respectively designate manual valve (M/V), pressure control valve-A (PCV-A), pressure control valve-B (PCV-B), shift control valve (SCV), rear clutch exhaust valve (R/C Ex-v), 2-3 and 3-4 shift valve (2-3 and 3-4 S/V), control shift valve (CSV) and fail safe valve (FSV).
In the auto transmission thus constructed of the prior art, when a driver wants to change the shift lever from the backward running xe2x80x98Rxe2x80x99 range to the forward running xe2x80x98Dxe2x80x99 range while the vehicle is running backwards at a low speed, the front clutch C2 and low reverse brake C3 function as combination elements to perform the backward running.
When a driver wants to change the shift lever to the forward running xe2x80x98Dxe2x80x99 range, the front clutch C2 and low reverse brake C3 are released, and the rear clutch C1 and kick down servo C5 function as combination elements to perform the forward running. At this time, a kick down band is firstly fastened with the supply of line pressure to the combined side of the kick down servo C5, and, then, the line pressure of the rear clutch C1 is gradually raised to complete the control of a shift to the second running speed of the vehicle.
However, there is a problem in the prior art in that severe rolling and shift shock occur by an instantly stopping vehicle as one way clutch (OWC) is turned to its reverse direction when the rear clutch is suddenly fastened to the kick down band of the kick down servo C5.
It is an object of the present invention to solve the aforementioned problems and provide a method for controlling shifts of an auto vehicle transmission to perform forward running after a forward running shift is determined in consideration of operational states such as a driver""s manipulation of a brake pedal, engine idle and backward running speed at the time of a Rxe2x86x92D range switch of the shift lever according to a backward driving driver""s intention to run forwards.
In order to accomplish the aforementioned object of the present invention, there is provided a method for controlling shifts of an auto vehicle transmission, the method comprising the steps of:
discriminating whether a Rxe2x86x92D range switch signal has been input while the vehicle is running backwards;
detecting the vehicle""s running state if the Rxe2x86x92D range switch signal has been input;
discriminating whether the first speed shifting conditions are satisfied when the detected running states of the vehicle have been determined as follows: a brake switch is turned off, and the running speed is greater than 0 Kph; and
performing the first shifting process if all the first speed shifting conditions have been fully satisfied.